let S1, S2 be non empty non void ManySortedSign ; for f, g being Function st f,g form_morphism_between S1,S2 holds
for A being MSAlgebra of S2
for o1 being OperSymbol of S1
for o2 being OperSymbol of S2 st o2 = g . o1 holds
Den o1,(A | S1,f,g) = Den o2,A
let f, g be Function; ( f,g form_morphism_between S1,S2 implies for A being MSAlgebra of S2
for o1 being OperSymbol of S1
for o2 being OperSymbol of S2 st o2 = g . o1 holds
Den o1,(A | S1,f,g) = Den o2,A )
assume A1:
f,g form_morphism_between S1,S2
; for A being MSAlgebra of S2
for o1 being OperSymbol of S1
for o2 being OperSymbol of S2 st o2 = g . o1 holds
Den o1,(A | S1,f,g) = Den o2,A
then reconsider g9 = g as Function of the carrier' of S1,the carrier' of S2 by Th10;
let A be MSAlgebra of S2; for o1 being OperSymbol of S1
for o2 being OperSymbol of S2 st o2 = g . o1 holds
Den o1,(A | S1,f,g) = Den o2,A
let o1 be OperSymbol of S1; for o2 being OperSymbol of S2 st o2 = g . o1 holds
Den o1,(A | S1,f,g) = Den o2,A
let o2 be OperSymbol of S2; ( o2 = g . o1 implies Den o1,(A | S1,f,g) = Den o2,A )
assume
o2 = g . o1
; Den o1,(A | S1,f,g) = Den o2,A
then the Charact of A . o2 =
(the Charact of A * g9) . o1
by FUNCT_2:21
.=
the Charact of (A | S1,f,g) . o1
by A1, Def3
;
hence
Den o1,(A | S1,f,g) = Den o2,A
; verum